I wish someone would put together the "basic math" resource for people like that. I didn't do any maths beyond 16. I was an maths idiot at school (me? the teacher? I dunno) but since then I've worked 20 years in programming and had to learn more and more maths just to make a living. However, my maths is a rickety hodge-podge house, with no real foundations. I can't be a total idiot, because I've done some decent work in distributed systems, even research in CRDTs (which made me learn some math) but still, I'd love a self-study plan that took me from 16 to today with the _real basics_.
Thanks for your comment, it made me feel less alone.
Such a thing exists
https://m.youtube.com/playlist?list=PL5A714C94D40392AB though he's using nonstandard notation it doesn't matter. His lectures are like learning lisp to better understand programming in general but for math. Combine them with a Sheldon Axler college algebra text or something.
Honestly, this is what Khan Academy is. Start at high school algebra and work your way up the skill tree. There is no shortcut though, so you won't find a single book that will teach you undergraduate level maths in a week.
Thanks for your comment, it made me feel less alone.